Olwen

Weapon: Dire Thunder
Support: Reposition/Ardent Sacrifice (if running Desperation)
Special: Moonbow/Draconic Aura/Galeforce
A: Life and Death 3/Darting Blow 3/Swift Sparrow 2
B: Watersweep 3/Windsweep 3/Desperation 3
C: Hone Cavalry/Fortify Cavalry/Threaten Res/Threaten Speed/Flexible
S: Phantom Speed/Speed+1/Attack+1/Quickened Pulse
Recommended Boon: Att+
Recommended Bane: HP-

Build cost: 2130

Locked behind 5* and lacking in attack compared to her infamous brother, Olwen is very often overlooked. I got Olwen back when Delthea was first added to the game in my desperate attempt to get the powerhouse mage. Considering I had an Attack Boon Reinhardt, Olwen never saw any use and I decided to change that.

In this build, Olwen is meant to abuse Watersweep, and is, in my opinion, the only unit who really can without crippling their ability to Quad attack. Most units who are fast enough to use it to duel other ranged attackers are Bridal Corelia, Brave Lyn, and various fast mages. Unfortunately, the two archers mentioned above are quad attackers and the fast mages like doubling their enemy.
Dire Thunder's two users aren't exactly amongst the fastest units. Reinhardt is at a miserable neutral 18 with Dire Thunder equipped and a speed neutral Olwen hits 29 with Dire Thunder. This makes Olwen the better user of Dire Thunder+Watersweep/Windsweep because she's just fast enough to make use of it.

Rather than taking Death Blow like her older brother, Olwen takes Life and Death. This is preferred over Swift Sparrow and Darting Blow as Swift Sparrow is extremely rare, being locked behind 3 5* exclusive units, one of them being event locked, and the other being lost in colorless hell. Life and Death completely negates Olwen's speed loss from Dire Thunder. Allowing her to hit 34 neutral speed. With Phantom Speed and Hone Cavalry, this allows her to hit 45 speed, thus cancelling a counter attack from most speedy mages with speed boons and Life and Death (if they aren't running the speed+1 seal or are merged). This also allows her to hit 40 attack (43 attack with a boon). Thus coming closer to matching Rein's attack power. While he has more raw power, Olwen can still cause some serious damage. Especially if she has any buffs.

For specials, Moonbow is taken for how quickly it charges, however, Draconic Aura works equally as well and is the special I usually prefer with brave weapon units.

Alternatively, Galeforce can be taken. An explanation provided by my friend explains why: Running either
Desperation or Sweep, QP Moonbow probably works best in Arena teams, but as an offensive unit, Galeforce is a better choice, especially in Tempest Trials. And combined with her Sweep skill allows her to Quad enemies that she normally woudn't be able to (super fasts) and kill more units without needing a dancer. True, most speedsters are fragile but that ain't the point. She's meant to Counter high-speed units. Rein's there to take out the slower ones that Olwen would normally Quad.

Good teammates for Olwen include Reinhardt, any other brave weapon user, anyone with Cavalry buff skills. The Renais Twins (Eirika and Ephraim) are also good for Olwen. Dancers also are wonderful for Olwen.

Counters to Rein also counter Olwen and with her physical defenses lacking and her HP being as low as it is, anything that gets a hit on her will likely kill her.

Despite the fact that Olwen has a respectable 30 Res without buffs, her low HP pool offsets her ability to take magic hits somewhat especially if she's a -HP or -Res, thus -Def is her preferred bane. With this in mind, keeping Life and Death on a +Spd Olwen, will further bolster her offensive capabilities while running her defenses to the gutter as she will opt to stay out of combat aside from initiation. Ardent Sacrifice is her Assist of choice to bring her into Desperation range.

Fully buffed Olwen still reaches a respectable 31 Res which does allow her to take a hit from a red mage if need be. Some might argue that Fury will allow her to do that better as she reaches 39 Res, but that would be later offset by the fact that they take 6 damage post combat.

Draconic Aura is her special of choice for more consistent damage output, and the fact that cooldown count for Specials aren't of too much concern for Blade tome wielders. With full buffs Olwen reaches 54 attack granting her 16 extra damage off of Draconic Aura. In the same train of though Olwen reaches 52 speed with full buffs.

Reinhardt generally pulls Dire Thunder of better than Olwen unless she also receives Goad Cavalry buffs, so it is entirely possible to use her as your main Dire Thunder attacker assuming she gets the buffs she needs. For the most part though, Olwen will be offensively inferior to her brother outside of Horse Emblem teams.

Dire Thunder is the magic version of a brave weapon. It attacks twice, but for the cost of 5 speed. It's broken on Reindhart, but Olwen needs a bit of work. This can be switched out for Blarblade, although you need to sacrifice 20000 feathers to get it.

Reposition is part of Olwen's base kit and is probably the best assist skill for her. It's not worth using 225 SP on getting another assist skill for her.

Olwen suffers from "Low attack syndrome" which means her attack is horrifyingly bad. At 26 neutral attack. With a -Atk Olwen, they're equivelant to Odin, one of the worst characters in the game. So the best way to resolve that is by buffing it by using Olwen's high enough resistance. Using Glacies, Olwen's attack is buffed by 24 which beats out Dragon Fang's 18. Although using Moonbow or Luna might be better, those require circumstances where Olwen actually does damage to work effectively. Using Glacies in my opinion is a better option.

Triangle Adept can help overcome Olwen's horrible attack; but only to red units. This is good because now she's a red killer and can kill more reds with ease. This also means she's more vulnerable to Green units. Life and Death can also help and Fury as well with probably less horrible consequences, but the attack boost is smaller; yet applies to all colors.

Desperation is usually overkill. It's rarely used on my Olwen tbh. Vantage can be used to further assault red mages and help kill archers or dagger users with low res.

Threaten Res is probably ideal if you want to deal extra damage to bow and dagger users. Olwen can beat a Brave Bow Takumi and Jaffar with Threaten Res. Olwen leaves Setsuna and Klein terribly injured. Without Threaten Res, Olwen is seriously injured from Takumi and doesn't kill him.

Seal : atk+1 or spd +1
IV : +atk -def
Merges : +2

With a 50/39 offensive spread with a single hone cavalry, Olwen will reach the same spread as neutral LnD Bridelia buffed by Eirika, the main differences is that she is on a horse, can actually tank a hit with that build, and
deals magical damage.
Pair her with a red horse that can take out green tome users and you have a very strong dual-core that can take out most of the meta

She usually OHKO every reds, every non +res blue tomes, every common lances (even effie!), and ORKO every common non TA axes (she needs Desperation to take out hector)
However she is still walled by Julia, and Fae (reminds me someone...) but she can actually kill sonya with desperation

Iceberg is usually the best choice as it add 17 damage on hit (Luna will deal less 95% of the time) and will be ready for the next initiation or if any ranged unit attacks her if you fail to quad

LnD 3 works too to transform her as a pure glasscannon that can even take out most of +res blue tome users but she loses the ability tank swords, some lances and some green tomes like Julia. LnD is needed to have fairly the same offensive power in a non horse emblem team. Draconic aura would be the best special (avoid Luna unless in Infernal maps, as most arena threats has less than 30 res)

UsInge this budget set I can clean out whole teams, glacies is amazing on this set as it can take down almost any character of any type, having quickened pulse helps a lot too